Problem: The scale on a map is 5cm : 6km. If the distance between two cities is 48km, how far apart in cm are the two cities on the map?
Solution: The scale means that every 5cm on the map corresponds to an actual distance of 6km. An actual distance of 48km is the same as 8 $\cdot$ 6km. The distance between the two cities on the map is 8 $\cdot$ 5cm, or 40cm.